1. Field of the Invention
The present invention relates to a bending apparatus, and more particularly to a bending apparatus suitable for bending pipes with a small bending radius.
2. Description of the Related Art
The use of smaller components in automobile engine compartments and cooling apparatus have increased in recent years, and demand is increasing for metal pipes which are bent to a small bending radius, for instance to a bending radius which is smaller than the diameter of the pipe, in order to connect between components which are tightly arranged.
As shown in FIG. 5 and FIG. 6, a conventional bending apparatus bends pipe 50 to a prescribed angle by interposing the pipe 50 between a bending die 51 and a clamping die 52, holding down the pipe 50 using a pressure die 53, and in this condition, rotating the bending die 51 and the clamping die 52 with the center O of the bend as the center of rotation.
However, when a bend with a tight bending radius is attempted with the aforementioned conventional bending apparatus, the outside wall 54a in the bending region 54 formed in the pipe 50 will be elongated, and there will be problems with flattening of the pipe and the wall thickness becoming extremely thin as shown in FIG. 6. In order to resolve these problems, a method to apply pressure in the direction of the bending region 54 of the pipe 50 while bending has been proposed, but in this case, buckling will occur in the pipe on the inside wall 54b of the bending region 54, so the appearance will be poor and the cross-section area of the pipe 50 will be significantly reduced in the bending region 54.
Therefore, as shown in FIG. 7, various types of correction cores 55 or the like are used after bending to correct the flattening or buckling, and in Japanese Patent Application Laid Open No. H6-262282, technology is disclosed which simultaneously processes the ends with a spool or a bulge or the like using an operation to correct the flattening or buckling of the pipe after the bending has been performed.
However, the aforementioned post-bending pipe correcting operation is an inconvenient operation, requires fabrication of a correction core 55 or the like, and increases the number of correction processes using the correction core 55, so the manufacturing costs of bent pipe will increase, and although the correcting process is performed at the same time as processing the ends with a spool or bulge as shown in Japanese Patent Application Laid Open No. H6-262282, preferably the operation would eliminated if possible.